Magnetodielectric coupling in MnCr2O4 spinel

We have investigated the magnetic and dielectric properties of polycrystalline samples of the spinel MnCr2O4. Below the ferrimagnetic ordering temperature at TN43 K, both magnetization and dielectric measurements show signatures of the onset of a conical structure at Ts17 K and a lock-in temperature at Tf14 K. These values are similar to those previously reported for single-crystal samples, where the spiral structure is short-range ordered (SRO) at low temperatures. The application of magnetic field suppresses the dielectric anomaly at Tf indicating that the coherence length of the ordering increases. MnCr2O4 exhibits a symmetrical magnetodielectric response between Tf and Ts that scales with the square of the magnetization. This suggests that the magnetodielectric coupling originates from the P2 M2 term in the free energy expansion. The magnetodielectric response becomes asymmetric with respect to field below Tf.